1. Field of the Invention
The present invention relates to an upper tool holder apparatus in a press brake, and more specifically relates to an upper tool holder apparatus in a press brake which is capable of easily detaching an upper tool from an upper table in the press brake so as to exchange it with new one.
2. Description of Relevant Art
A press brake has an upper table (called also as an upper apron) and a lower table (called also as a lower apron). The upper table and the lower table are arranged in an up-and-down direction so as to face each other. One of the upper table and the lower table is suitably driven up and down as a ram.
In order that the press brake having the above structure bends a plate-shaped workpiece, a lower tool (die) is mounted to an upper portion of the lower table, and an upper tool (punch) is mounted to a lower portion of the upper table.
In the above structure, after the workpiece is located on the die, the upper tool and the lower tool are engaged with each other so that the workpiece can be bent.
Incidentally, when a forward end (lower end) of the upper tool provided on the upper table via an upper tool holder apparatus is brought into contact with a V groove formed in the lower tool so that an origin is set in the press brake with a pressure of 2 to 3 t, for example, being applied, the upper tool is broken in the case where a length of the upper tool is short. For this reason, conventionally an operator lifts the upper tool so as to set the origin, and thus this operation is hard.
In addition, since the upper tool is exchanged in the press brake because of a difference in forms of bent workpieces, for example, a lot of upper tool holder apparatuses are mounted to the lower portion of the upper table, and the upper tool holder apparatuses support the upper tool to the upper table detachably.
The conventional upper tool holder apparatus is constituted so as to mount an upper tool clamp to a holder main body mounted to the lower portion of the upper table via a clamping bolt to be oscillated and firmly fix the upper portion of the upper tool inserted between the upper tool clamp and the holder main body via the upper tool clamp by clamping the clamping bolt.
Incidentally, since the above-mentioned conventional upper tool holder apparatus detaches the upper tool from the upper table to exchange it even if the length of the upper tool is short, a lot of the clamping bolts provided in the upper tool holder apparatus should be operated. As a result, this operation is extremely troublesome. Moreover, since a long wedge member is provided in a right-and-left direction between the upper table and lower tool holder apparatus in order to adjust the height of the upper tool, crowning in a longitudinal direction of the upper tool cannot be adjusted fine.